1. Field of the Invention
This invention relates to an optical recorder in which optical recording is carried out by means of a plurality of laser beams.
2. Description of the Related Art
An optical recorder which effects optical recording by scanning by a plurality of laser beams is well known such as disclosed in Examined Japanese Patent Publication. No. Sho 60-33019. A general optical recorder of this type will be explained with reference to FIG. 1. A plurality of laser beams 43 emitted from a semiconductor laser array 41 are reflected from a polygon mirror 44 into rows of minute optical spots 48, and these optical spots 48 are simultaneously swept over a photosensitive drum 47. In the drawings, reference numerals 42 and 45 designate lenses. A photosensor 46, provided in the vicinity of the end of the photosensitive drum 47, detects the positions of the plurality of laser beams 43, which are to be swept at one time, in the direction of scan. The position of scanning is controlled by means of a controller 49 using the sensing signal as a synchronous signal.
Intervals between the rows of optical spots 48 are usually larger than required scanning line pitch, and hence it is necessary to arrange the optical spots 48 in rows on the photosensitive drum 47 at an inclined angle with respect to the scan direction. This makes the scanning intervals of the optical spots equal to the scanning line pitch. In this way, it is possible to adjust the scanning line pitch by changing the inclined angle of the optical spots 48 in rows.
However, in this type of system wherein the rows of the optical spot are set at an inclined angle with respect to the scan direction, the plurality of laser beams to be simultaneously swept respectively have different positions in the scan direction. For this reason, a complex controller is required to effect optical recording by correcting the scanning positions of the laser beams and aligning the scanning positions with high accuracy.